Undiagnosed sources of pain are a frequent, though often a nonspecific presenting symptom of numerous medical conditions. A classic attempt to make pain a more specific diagnostic in conjunction with anatomical knowledge is when the Doctor palpates a particular part of the body and asks does this hurt? This works well enough for potential sources of pain at or near the surface of the skin that are on the same scale as the Doctor s fingers. Yet there remains a need to more precisely, reliably and in a noninvasive manner, stimulate individual constituent pieces of a complex structure within the body (i.e., the disks, vertebral body, lamina and facets of the spine) so as to identify the exact source of pain. It is well known that high-intensity focused ultrasound (HIFU) can focally, non-invasively and without damage probe small structures, including those within the body, via the induction of small displacements within tissue by inducing local temperature changes in tissue. Our long-term goal is to develop a new diagnostic tool for the physician by increasing the specificity of pain through the non-destructive use of image guided HIFU. In essence, we propose to use noninvasive, focal ultrasound to differentially diagnose back pain by the non-invasive and safe stimulation of individual potential sources of back pain and subsequently reported patient responses through the focal induction of displacement and/or increases in temperature of relevant tissue by HIFU. We call this TAP for Transcutaneous Acoustic Palpation [unreadable] [unreadable]